Intravenous fluids are generally supplied to the patient under the force of gravity by positioning a reservoir containing an I.V. liquid reservoir at atmospheric pressure at an elevated position relative to the patient. The rate of flow is set by a manually adjustable valve connected in the line between the reservoir and the patient, and once set, the rate remains essentially constant as long as the head of liquid does not change appreciably. Of course, as the liquid is being fed to the patient the pressure head slowly decreases causing the flow rate to decrease proportionately, and if a precise amount of liquid is to be supplied to the patient this change must be taken into account when the valve is initially set or in the alternative the manual valve can be reset from time to time. However, should the patient roll over or make some other movement which appreciably changes the vertical distance between the reservoir and the cannula the flow rate changes more dramatically.
It would be desirable to provide an I.V. system wherein the I.V. fluid reservoir is pressurized and wherein the fluid is supplied to the patient at a substantially precise preset rate irrespective of changes in the pressure head of fluid above the patient. It would also be desirable to include in such a system means for interrupting the supply of I.V. fluid once a preset volume of fluid has been administered to the patient, and to provide an alarm responsive to changes in the pressure feed rate and volume for attracting a nurse or physician when they are needed.